High pressure liquid chromatography (HPLC) and ion chromatography (IC) generally require the components of a sample to be separated or analyzed be dissolved in a mobile phase liquid, termed an eluent, and conveyed by that liquid to a stationary phase, that is, a separation column. The separated components may then by analyzed by a conductivity detector downstream from the stationary phase. Piston pumps are often used to supply the liquid and deliver the liquid, with dissolved sample, to the separation column. Such piston pumps are used to withstand extreme pressures and to deliver the liquid at precisely controlled flow rates in a smooth and uniform manner.
In HPLC, such piston pumps may generally include a pump head that have one or more plungers formed of conductive materials such as stainless steel. In IC, such piston pumps generally include pump heads that have one or more plungers formed of non-conductive materials such as sapphire or ceramics. The pump heads also include special high pressure seals that may have lips pressed against the plunger surface by the pressure built up in the pump head, that is, the system pressure. Such pressure seals are described in U.S. Pat. No. 6,623,630 to Staffler, and in U.S. Pat. No. 6,918,595 to Proper.
As the piston moves to aspirate new eluent, small amounts of eluent residing in the head chamber of the pump are commonly transported by the piston surface through the seal to the backside of the seal. Accordingly, such piston pumps often include a wash chamber on the backside of the seal to flush any leakage through the seal. Such wash chambers are generally filled with an aqueous wash solution, which may prevent the growth of salt crystals on the rear side of the seal. The wash solution is sometimes spiked with organic solvent. This organic addition to the wash solution prevents growth of algae and fungi inside the wash chamber.
A voltage potential may be created by the piston moving against the seal and/or by a battery effect from micro-leakage of the seal. Such voltage potential may undesirably bias the conductivity detector causing unwanted noise on the signal baseline.
In light of the foregoing, it would be beneficial to have systems and apparatuses that overcome the above and other disadvantages of currently available chromatography systems utilizing conductivity detectors and piston pumps.